When Dr. Peter Venkman and his Columbia University colleagues Dr. Raymond Stantz and Dr. Egon Spengler are kicked out of their prestigious academic posts, they start a private practice as professional ghost-catchers.
Although the three parascientists are idle for a while, their television advertisements finally pay off when beautiful Dana Barrett contracts them. It seems her apartment has become the entryway for ghastly ghosts and goofy ghouls hellbent on terrorizing New York City.
Armed with proton guns, the Ghostbusters become wildly popular, and they are joined by Winston Zeddmore who is looking for a job with good pay. Overzealous Environmental Protection Agency (EPA) agent Walter Peck thinks the Ghostbusters are frauds, and he has the Ghostbusters put in jail.
Peck is forced to believe the Ghostbusters when New York City is put under siege by an ancient Sumerian God named Gozer the Gozerian, who is channeled through the building that Dana Barrett and Louis Tully live in, and the mayor has no choice but to let the Ghostbusters out of jail to face Gozer.